MRI for nodal restaging after neoadjuvant therapy in rectal cancer with histopathologic comparison

Abstract

Background After neoadjuvant therapy, most of the lymph nodes (LNs) will shrink and disappear in patients with rectal cancer. However, LNs that are still detectable on MRI carry a risk of metastasis. This study aimed to evaluate the performance of the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) criterion (short-axis diameter ≥ 5 mm) in diagnosing malignant LNs in patients with rectal cancer after neoadjuvant therapy, and whether nodal morphological characteristics (including shape, border, signal homogeneity, and enhancement homogeneity) could improve the diagnostic efficiency for LNs ≥ 5 mm. Methods This retrospective study included 90 patients with locally advanced rectal cancer who underwent surgery after neoadjuvant therapy and performed preoperative MRI. Two radiologists independently measured the short-axis diameter of LNs and evaluated the morphological characteristics of LNs ≥ 5 mm in consensus. With a per node comparison with histopathology as the reference standard, a ROC curve was performed to evaluate the diagnostic performance of the size criterion. For categorical variables, either a χ2 test or Fisher’s exact test was used. Results A total of 298 LNs were evaluated. The AUC for nodal size in determining nodal status was 0.81. With a size cutoff value of 5 mm, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 65.9%, 87.0%, 46.8%, 93.6% and 83.9%, respectively. No significant differences were observed in any of the morphological characteristics between benign and malignant LNs ≥ 5 mm (all P > 0.05). Conclusions The ESGAR criterion demonstrated moderate diagnostic performance in identifying malignant LNs in patients with rectal cancer after neoadjuvant therapy. It was effective in determining the status of LNs < 5 mm but not for LNs ≥ 5 mm, and the diagnostic efficiency could not be improved by considering nodal morphological characteristics.

Comparison of preoperative CT- and MRI-based multiparametric radiomics in the prediction of lymph node metastasis in rectal cancer

“…In clinical practice, acquiring T2WI images instead of CE-T1WI images can avoid adverse effects caused by contrast agents to reduces medical risks and medical expenses. Additionally, it is generally believed that T2WI is preferred for the morphological evaluation of LN while CE-T1WI provides minimal benefit for the accurate determination of metastatic nodes in RC (27). Thus, our study provides a further rationale for the fact that T2WI is often used as an optimal sequence in constructing radiomics model to predict LNM in RC (28)(29)(30).…”

MRI Evaluation of Rectal Cancer Lymph Node Staging Using Apparent Diffusion Coefficient

“…Many studies have shown that after neoadjuvant therapy, the count of lymph nodes typically reduces, and the short-axis diameter either diminishes or vanishes entirely; this shows nodal downstaging [ 24 ]. Most of our study patients in the CT group (67.5%) before treatment were staged at N2.…”